Lego books are probably in short supply, so I'm thinking we go with a standard 1:1 rotation. You're going to need to learn how speed tuning works, and I'm not going to go too much into details on that here, but 1:1 rotation means you want everyone to be between 170 and 189 speed, so that the tune can work for both NM and UNM.

Mausoleum Mage (Block Debuffs) - MAKE SURE HE IS SLOWEST. On green CB, make sure he uses his A2 before the second attack, and on non-green CB, make sure he uses it before the stun. 

Giscard (DEF up, backup ATK down) - MAKE SURE he is second slowest.

Corpse Collector (Leech, poison) - turn off A2

Geomancer (HP Burn, Weaken, passive) - set A3 on priority. On green CB MAKE SURE HE IS LEAD, since he needs to take the stun instead of Maus Mage.

Tayrel (primary ATK down, DEF down) - turn off A3

It's not perfect - in particular, you're pretty vulnerable against red CB, since only Giscard is going to reliably place ATK down, and his ATK down has only a 75% chance of landing. Still, between him and Tayrel hopefully you can keep it active. You have a *ton* of champs who could be useful for CB, but they are lego, and very much need books to be useful.

How close are you to fusing Mikage? Ninja + Rathalos might be a combo that'll get you way more damage, especially if you can pair Mikage. I think your champs you've built would be better served on a Normal Hydra Team for all the HP Burn you want to do (Artak+Sicia) as well as Uugo because of how her ability, and Sicias, works based on # of targes. How about Arbiter?

Get Rathalos to 60 as fast as you can followed by Ninja. Also get Geomancer out of the vault and get him to 60 too!

The HP Burn/Poison/Max HP attacks route you seem to want to go isn't as effective as you might think, it requires surviving many many rounds to really build up. 

I'll do 2 Builds for you. First will be based on what you should go for, Second will be a Hydra Team based on who you have currently:

1.  Rathalos, Geomancer, Scyl, Apothecary and Giscard. (This covers Dec Def, Weaken and Dec atk on boss with Inc Speed, Inc Def and Inc Atk on team)

2. Sicia, Artak, Uugo, Rathalos, Scyl and Giscard.

Now if you get Arbiter or Mikage, we can change some champs around in both teams possibly

Thank you guys for the support, @kramaswamy.kr and @Onikage55 

I am quite far away from Arbiter and Mikage to be honest.

Regarding the speed tune, I did some research and created a table :

I just got 1* Blessing for Tayrel  ( Should I put him on Cruelty ? )

I am close to fuse Rhazin that`s the closest fusion for the moment, Cuz I will win 2 legendary books as 1st place, possibly 3 legendary books.

This is an update from yesterday to today: I managed to level up the champions you recommended.

Tayrel / Mausoleum / Apotechary to 6*

Giscard / Geomancer and Corpse 5*

Deck of Fate event , I am able to Flip 30 cards , I hope I get lucky.

Champion Chase currently I am wining , 3 Legendary books will be achieved and as well new legendary Hansel , but I don't have Greta so he can stay in Vault.

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Mausoleum Mage:

• Turn A2 on manual to align it properly with Clan Boss attacks:
  • Green Clan Boss: Use A2 before the second attack.
  • Non-Green Clan Boss: Use A2 before the stun.
• Build Focus: Speed  HP/DEF (for survivability) > Resistance.

Giscard the Sigiled:

• Ensure DEF Up and backup ATK Down (A1) are applied consistently.
• Build Focus: Speed  DEF  Accuracy (for ATK Down).

Corpse Collector:

• Turn A2 off in AI settings.
• Focus on Leech (A1) and Poison (A3) uptime.
• Build Focus: Speed  Accuracy  HP/DEF.

Geomancer:

• Priority A3 (HP Burn/Weaken). Stun-taker on Green CB.
• Build Focus: Speed  HP  Accuracy.

Tayrel:

• Turn off A3 to avoid misalignment.
• Primary focus on ATK Down (A1) and DEF Down (A2).
• Build Focus: Speed  DEF  Accuracy. 

Example Gear Sets:

• Mausoleum Mage: Speed + Immortal/Deflection ( I have one set of deflection)
• Giscard the Sigiled: Speed + Lifesteal ( I have lifesteal good enough )
• Corpse Collector: Speed + Accuracy/Immortal ( Same here for Corpse )
• Geomancer: Speed + Perception/Lifesteal ( I have lifesteal good enough and Perception )
• Tayrel: Speed + Accuracy/Lifesteal  ( I have lifesteal good enough and Perception )

Hi @kramaswamy.kr and @Onikage55 

I just got lucky from 20 rare shards to pull Warchief as Legendary / Hoskarul / Fahrakin the Fat ( Burner and Poisoner ), Quargan the Crowned, Kunoichi and Delver.

Fahraking is a good option for Demon Lord but .... I should keep the composition that you suggested because Corpse brings the Leech debuff.